Zeolite p aluminosilicates and their manufacture and use in detergent compositions

ABSTRACT

P-type zeolite having the oxide formula M 2/n , Al 2 O 3 , (1.8-2.66) SiO 2 , y H 2 O and having a Calcium Binding Capacity of between 100 and 145 mg/g, preferably between 110 and 140 and a Calcium uptake rate of between 12 and 100 seconds, preferably below 50 seconds can be prepared from metakaolin.

FIELD OF THE INVENTION

[0001] The invention relates to crystalline aluminosilicates having the P-structure and to a process for manufacturing the same. These materials are of value as a component in detergent formulations in which they remove calcium and magnesium hardness ions by ion exchange. They also have other properties which provide additional benefits when used in detergent formulations. These aluminosilicates will be referred to as zeolite P in this description.

BACKGROUND OF THE INVENTION

[0002] While the utility of zeolite P in detergent formulations has been acknowledged, for example in European Patent Application 0384070 (Unilever), they must be manufactured by a commercially effective process in order to become available on the market place. Thus, while the properties of a material may make it a useful commercial commodity, its manufacture has to be optimised for large scale production.

[0003] The zeolite P class includes a series of synthetic zeolite phases which may be in cubic configuration (also termed B or P_(c)) or tetragonal configuration (also termed P₁) but is not limited to these forms. The structure and characteristics of the zeolite P class are given in “Zeolite Molecular Sieves” of Donald W Breck (published 1974 and 1984 by Robert E Krieger of Florida USA). The zeolite P class has the typical oxide formula:

M_(2/n)O. Al₂O₃. 1.80-5.00 SiO₂. 5H₂O

[0004] M is an n-valent cation which for this invention is an alkali-metal, that is lithium, potassium, sodium, caesium or rubidium with sodium and potassium being preferred and sodium being the cation normally used in commercial processes.

[0005] Thus sodium may be present as the major cation with another alkali metal present in a minor proportion to provide a specific benefit.

[0006] In EP-A-565,364 is described a process for preparing P zeolites in which aluminate and silicate solutions are reacted in presence of P zeolite seeds. During the formation of the crystalline zeolite the reacted medium passes through a gel stage. This process enables the production of high quality detergent zeolites having a Calcium Effective Binding Capacity (CEBC) of above 146 mg/g, with outstanding Calcium Uptake Rate (CUR) and high oil absorption.

[0007] In some applications it can be considered to use detergent zeolites with lower detergent characteristics but high oil absorption.

[0008] In U.S. Pat. No. 3,112,176 is described a process in which P type zeolites are produced from metakaolin. Having reproduced the examples disclosed in this document, a maximum Calcium Effective Binding Capacity of 90 mg/g has been obtained. Moreover, the kinetics characteristics of these zeolites were found to be very poor with a Calcium Uptake Rate of above 500 seconds.

[0009] In U.S. Pat. No. 3,008,803 is described a process in which aluminium hydroxide, silicic acid and water are mixed in a vessel and allowed to react at 100° C. for 48 hours with stirring. The agitation is stopped and the mixture is maintained at 100° C. for an additional 71 hours. A P-type zeolite with a CEBC of 65 mg/g and a CUR of above 500 seconds was obtained.

[0010] Now, to be used in detergents applications, a zeolite must exhibit, on top of a good CEBC (at least 100 mg/g), a Calcium Uptake Rate of less than 100 seconds. Therefore the zeolites P disclosed in U.S. Pat. No. 3,112,176 and U.S. Pat. No. 3,008,803 are not suitable for detergent applications.

[0011] There is therefore a need for a P-type zeolite with good detergents characteristics (i.e CEBC above 100 mg/g and CUR below 100 seconds) intermediate between those disclosed in U.S. Pat. No. 3,112,176 on the one hand and those disclosed in EP0384070 on the other hand. For the time being, it has not been possible to obtain such a P-type zeolite.

[0012] It has now been discovered that it is possible to obtain such an intermediate zeolite.

GENERAL DESCRIPTION OF THE INVENTION

[0013] It is a first object of the present invention to provide a P-type zeolite having the oxide formula:

M_(2/n), Al₂O₃, (1.8-2.66) SiO₂ , yH₂O

[0014] having a Calcium Effective Binding Capacity of between 100 and 145 mg/g, preferably between 110 and 140, most preferably between 110 and 130 mg/g and a Calcium uptake rate of between 12 and 100 seconds, preferably below 50 seconds.

[0015] Preferably, the P-type zeolite has an Average Particle Size of between 1 and 10 μm, more preferably between 3 μm and 6 μm.

[0016] It is a second object of the present invention to provide a process for manufacturing a P-type zeolite wherein metakaolin is allowed to react with a caustic solution in presence of P-type seeds.

[0017] The sources of the seed zeolite P is not critical, although preferably it is added to the reactants as a previously prepared slurry. Alternatively a crystallised slurry from a previous reaction may be used. Additionally the ratio of the P-zeolite seed is not critical and a P-zeolite having a Si:Al ratio above 1.33 can be used.

[0018] Preferably a caustic solution is first added into a reactor tank to form a caustic pool, metakaolin being then added to the caustic pool. The caustic pool is heated up to a temperature between 80° C. and 100° C., preferably above 90° C., before adding the metakaolin. More preferably metakaolin is added to the caustic pool in a slurry form.

[0019] The metakaolin can have a SiO₂/Al₂O₃ molar ratio of 2 to 2.5, typically ratios of 2.15 to 2.2 are easily commercially available.

[0020] The zeolite P seeds are added to the caustic pool 5 to 20 minutes after the addition of metakaolin preferably they are added to the caustic pool 10 to 15 minutes after the addition of metakaolin.

[0021] It is a third object of the present invention to provide a detergent composition comprising 0.5% to 60% by weight of a surfactant system, 20% to 80% by weight of a detergency builder system, and optionally other conventional components; the detergency builder system comprising, in an amount of 5% to 80% by weight of the detergent composition, an alkali metal aluminosilicate of the zeolite P type having a silicon to aluminium ratio not greater than 1.33, the aluminosilicate having a Calcium Effective Binding Capacity of between 100 and 145 mg CaO per g of anhydrous aluminosilicate, preferably between 110 and 140 and a Calcium uptake rate of between 12 and 100 seconds, preferably below 50 seconds.

Standard Procedures

[0022] In the characterisation of the zeolite-P materials prepared by the present process the following methods were used.

[0023] i. Particle size: The average particle size (microns) was measured by a Malvern Mastersizer (Trade Mark) obtainable from Malvern Instruments, England and expressed as the d₅₀, i.e. 50% by weight of the particles have a diameter smaller than the diameter quoted. The definitions d₈₀ and d₉₀ may also be used in association with the appropriate figure. Prior to measuring the particle size, the sample is dried as a thin layer (about 1.5 mm) at 110° C. for two hours in a fan oven.

[0024] ii. Calcium uptake rate (CUR): The rate of removal of Ca⁺⁺ ions from a wash liquor is an important characteristic of a detergency builder. The time, in seconds, is determined for a zeolite, at a concentration of 1.48 gdm⁻³ and a temperature of 25° C., to reduce the calcium ion concentration in a 0.01M sodium chloride solution from an initial value of 2×10⁻³ M to 10⁻⁵M. The zeolite was first equilibrated to constant weight over saturated sodium chloride solution and the water content measured.

[0025] iii. Calcium effective binding capacity (CEBC): The CEBC was measured in the presence of a background electrolyte to provide a realistic indicator of calcium ion uptake in a wash liquor environment. A sample of each zeolite was first equilibrated to constant weight over saturated sodium chloride solution and the water content measured. Each equilibrated sample was dispersed in water (1 cm³) in an amount corresponding to 1 g dm⁻³ (dry), and the resulting dispersion (1 cm³) was injected into a stirred solution, consisting of 0.01M NaCl solution (50 cm³) and 0.05M CaCl₂ (3.923 cm³), therefore producing a solution of total volume 54.923 cm³. This corresponded to a concentration of 200 mg CaO per liter, i.e. just greater than the theoretical maximum amount (197 mg) that can be taken up by a zeolite of Si:Al ratio 1.00. The change in Ca²⁺ ion concentration was measured by using a Ca²⁺ ion selective electrode, the final reading being taken after 15 minutes. The temperature was maintained at 25° C. throughout. The Ca²⁺ ion concentration measured was subtracted from the initial concentration, to give the effective calcium binding capacity of the zeolite sample as mg CaO/g zeolite.

[0026] iv. Oil absorption: This was determined by the ASTM spatula rub-out method (American of Test Material Standards D281). The test is based on the principle of mixing linseed oil with the particulate zeolite by rubbing with a spatula on a smooth surface until a stiff putty like paste is formed which will not break or separate when it is cut with the spatula. The weight of oil used is then put into the equation: $\begin{matrix} {{{Oil}\quad {absorption}\quad ({OA})} = \frac{g\quad {oil}\quad {absorbed} \times 100}{{{wt}.\quad {of}}\quad {zeolite}\quad ({gms})}} \\ {= {g\quad {{oil}/100}\quad g\quad {zeolite}}} \end{matrix}$

[0027] In order to measure the oil absorption of the product, the washed filter cakes obtained after crystallisation were merely dried at room temperature as a thin layer of about 2 mm until a solids content of at least 78% by weight was achieved, normally it was achieved in 2-3 days.

[0028] V. The form of the zeolite which was produced was established using standard XRD method.

SPECIFIC DESCRIPTION OF THE INVENTION

[0029] Examples of processes of the invention will now be given to illustrate but not limit the invention.

EXAMPLE 1

[0030] 2037 g of a 9.2% caustic solution was placed in a baffled 5 liter flask. The caustic solution was stirred and the temperature raised to 100° C. To the stirred solution, 186.5 g of metakaolin having a SiO₂/Al₂O₃ ratio of 2.18 (obtainable from English China Clay), slurried in 400 g of water, was added. The temperature and stirring was maintained for 5 hours, after which the product was filtered, washed and dried.

EXAMPLE 2

[0031] Example 1 was reproduced except that 20 g of P-type zeolite slurried in 30 g of water was added 15 minutes after the addition of the metakaolin/water slurry.

EXAMPLE 3

[0032] The procedure of Example 1 was repeated, except that 1930 g of 14.5% caustic solution and 300 g of metakaolin slurried in 600 g of water were used.

EXAMPLE 4

[0033] Example 3 was reproduced except that 20 g of P-type zeolite slurried in 30 g of water was added 15 minutes after the addition of the metakaolin/water slurry.

EXAMPLE 5

[0034] The procedure of Example 1 was repeated, except that 1800 g of 19.3% caustic solution and 400 g of metakaolin slurried in 800 g of water were used.

EXAMPLE 6

[0035] Example 5 was reproduced except that 20 g of P-type zeolite slurried in 30 g of water was added 15 minutes after the addition of the metakaolin/water slurry.

[0036] The products obtained in Examples 1 to 6 were analyzed and the results are summarized in the following table. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 XRD P + P P + A P A P (zeolite trace type) A APS (μm) 5 4.6 6.5 4.4 9.0 4.1 CUR 255 62 212 27 150 25 (seconds) CEBC (mg/g) 110 130 105 140 110 145 Oil 85 87 82 92 78 100 absorption capacity (g/100 g) 

1. P-type zeolite having the oxide formula: M_(2/n), Al₂O₃, (1.8-2.66) SiO₂ , yH₂O having a calcium effective binding capacity of between 100 and 145 mg/g and a calcium uptake rate of between 12 and 100 seconds:
 2. P-type zeolite according to claim 1 having an Average Particle Size of between 1 and 10 μm.
 3. Process for manufacturing a P-type zeolite wherein metakaolin is allowed to react with a caustic solution in presence of P-type seeds.
 4. Process according to claim 3 wherein a caustic solution is first added into a reactor tank to form a caustic pool, metakaolin being then added to the caustic pool.
 5. Process according to claim 3 or 4 wherein the caustic pool is heated up to a temperature between 80° and 100° C. before adding the metakaolin.
 6. Process according to claim 4 wherein metakaolin is added to the caustic pool in a slurry form.
 7. Process according to claim 3 or 4 wherein zeolite P seeds are added to the caustic pool 5 to 20 minutes after the addition of metakaolin.
 8. Process according to claim 7 wherein zeolite P seeds are added to the caustic pool 10 to 15 minutes after the addition of metakaolin.
 9. Detergent composition comprising 0.5% to 60% by weight of a surfactant system, 20% to 80% by weight of a detergency builder system, and optionally other conventional components; the detergency builder system comprising, in an amount of 5% to 80% by weight of the detergent composition, an alkali metal aluminosilicate of the zeolite P type having a silicon to aluminium ratio not greater than 1.33, the aluminosilicate having a Calcium Effective Binding Capacity of between 100 and 145 mg CaO per g of anhydrous aluminosilicate, preferably between 110 and 140 and a Calcium uptake rate of between 12 and 100 seconds, preferably below 50 seconds. 